One prior art structure of a fuel cell stack mountable on a vehicle has a cell laminate obtained by alternately stacking plates with the function of a power generation assembly and plates with the function of a separator. The fuel cell stack of this prior art structure has a problem of low resistance against an inertial load in a direction (may be referred to as ‘in-plane direction’ in the description herein) perpendicular to a stacking direction of the respective plates (may be simply referred to as ‘stacking direction’ in the description herein). Each plate generates a drag in a plane-pressing direction against an inertial load in the stacking direction, while generating a drag from a frictional force acting on an interface between each adjacent pair of plates against the inertial load in the in-plane direction. One proposed structure as disclosed in JP-A-2006-108009 forms a recess along the periphery of each plate and uses a casing with a specific mating shape with the recess to prevent a potential displacement of the plate in the in-plane direction.